Software Engineer II

Mattermost

Location: Germany
Job Type: full-time
Salary: Unknown
Posted: September 16, 2025

Job Description

At Mattermost, we build the #1 collaborative workflow solution for defense, intelligence, security, and critical infrastructure organizations. Trusted by governments, financial institutions, and technology companies, our platform enables secure, efficient operations for the world’s most critical teams.

We’re dedicated to empowering organizations to operate with confidence, reducing risks, and accelerating productivity. Guided by our core values of Customer Obsession, Earn Trust, Self Awareness, Ownership and High Impact, we collaborate closely with our customers to deliver solutions that meet complex needs and drive success.

Mattermost is seeking a highly skilled and experienced Software Engineer II to design, develop, and maintain cutting-edge solutions that enable secure, efficient, and collaborative workflows for mission-critical industries like defence, intelligence, and critical infrastructure.

As a Software Engineer II, you'll work at the intersection of technology and user needs, delivering features that solve real-world problems, particularly in domains where precision, security, and collaboration are paramount. This is more than a coding role—it’s a product engineering role focused on building products with a direct impact on critical workflows. Your contributions to our open-core platform using your personal GitHub account will empower the broader developer community while leaving a lasting professional legacy.

The person in this role will join a fast-paced, flexible full stack team responsible for developing and delivering impactful features and systems that empower collaboration for the world’s most critical organisations. Do you have a passion for designing and developing high-impact products? Do you want to work with a well-oiled, collaborative and highly senior team? Do you want to make an impact on open source? Help us build and grow one of the largest React and Go open-source projects.

Responsibilities include:

Design, build, and maintain software solutions using TypeScript, React, React Native, and Go to deliver secure and scalable products
Take full-stack ownership by developing user-facing features, back-end architectures, APIs, and integrations
Contribute to Mattermost’s open-source platform through GitHub, creating impactful open-source solutions for both internal and external ecosystems
Collaborate with product managers, designers, and engineers to prototype and ship tailored solutions for complex workflows
Mentor peers through code reviews, technical discussions, and knowledge sharing, fostering a culture of excellence
Implement and maintain unit/integration/e2e tests to ensure code quality and robust platform performance
Diagnose and resolve bugs or performance bottlenecks, ensuring security and reliability in deployments
Leverage customer and industry feedback to iterate rapidly and deliver adaptable, high-value solutions
Lead the development of mission-critical, customer-focused solutions, anticipating the evolving needs of defence, intelligence, and infrastructure industries

Requirements

BS in Computer Science, Computer Engineering, or related field/experience
3+ years of experience working as a full-stack software engineer building scalable, production-ready systems
Strong skills in our technology stack: TypeScript, React, React Native, Go, and/or PostgreSQL
Expertise in full-stack development, including designing APIs, implementing frontends, creating fault-tolerant back-end code, and optimising database performance
Enthusiasm for and experience developing with AI tools like Claude Code, Cursor and/or GitHub Copilot
Solid understanding of modern development workflows, including CI/CD pipelines, distributed systems, and cloud infrastructure
Comfortable working as a product engineer, focused on solving customer-centric problems in addition to writing code
Strong written and verbal communication skills suitable for diverse audiences
Capable of working independently across multiple time zones while actively engaging in team collaboration

Preferences

Experience contributing to open-source projects
Experience with end-to-end testing frameworks such as Playwright and/or Cypress
Expertise in defence, intelligence, or security-focused workflows
Has worked fully remotely with global teams

Mattermost takes a market-based approach to pay and pay may vary depending on your location. The successful candidate’s starting pay will be determined based on job-related skills, experience, qualifications, work location, and market conditions. These ranges may be modified in the future.

Mattermost is an EEO Employer, we are a remote-first, open-source company.

We are continually working to expand our hiring in more countries and regions, ensuring compliance with local laws and regulations, which takes time.

Mattermost values your unique perspective—we welcome all applicants. We encourage individuals from all backgrounds to apply and are committed to assessing candidates based on their skills and qualifications. We do not tolerate discrimination against staff or applicants based on race, religion, national origin, age, disability, pregnancy status, veteran status, or other personal characteristics.

If you require accommodations during the interview process, please let us know—we’re happy to assist.

🎯 Who is this job for?

This position is ideal for a Mid-Level Full-Stack Software Engineer with 3+ years of experience in TypeScript, React, React Native, and Go, with a focus on secure, scalable systems. Candidates should be comfortable with API design, database optimization (PostgreSQL), CI/CD workflows, and contributing to open-source projects. Familiarity with AI development tools, remote collaboration, and customer-focused product engineering is a strong plus.

💬 Potential Interview Questions

How would you design a versioned API between a Go backend and TypeScript clients (web and React Native)?
Prefer gRPC/Protobuf for internal services and REST for public clients, with semantic versioning and backward-compatible changes. Use an API gateway for auth/rate limits and generate TS clients from OpenAPI/Protobuf to avoid drift.
How do you prevent goroutine leaks and ensure graceful shutdowns in Go services?
Propagate context.Context through all call chains, select on <-ctx.Done() in workers, and close channels. Tie servers and background jobs to a parent context and handle SIGTERM with time-bounded shutdown.
What Postgres techniques do you apply to keep high read/write throughput?
Create covering/composite indexes that match query filters and sort order, monitor with EXPLAIN ANALYZE, and use partitioning for large time-series tables. Keep transactions short and use connection pooling (e.g., pgbouncer).
How do you secure auth across web and mobile clients?
Use OAuth2/OIDC with short-lived tokens and refresh flows; store tokens in secure storage (Web: httpOnly cookies + CSRF protection; RN: Keychain/Keystore). Enforce mTLS service-to-service and rotate secrets via a vault.
How do you keep a large React app responsive under heavy state changes?
Split server cache from UI state (React Query/SWR), use React 18 concurrency (useTransition, useDeferredValue), memoize selectors, and virtualize long lists. Avoid prop drilling with context boundaries and memo.
What are best practices for React Native performance and reliability?
Enable Hermes, minimize bridge traffic by batching/using JSI modules, and cache images/assets. Implement offline-first with normalized stores and background sync, and guard views with error boundaries.
How do you design CI/CD for a full-stack repo (Go + TS) with high confidence and speed?
Pipeline stages: type/lint → unit → integration (Testcontainers) → e2e (Playwright) → build/sign images → deploy canary with auto-rollback on SLO breaches. Use feature flags and backward-compatible DB migrations.
How would you implement observability end-to-end for mission-critical workflows?
Adopt OpenTelemetry for traces/metrics/logs with correlation IDs from client → API → DB. Define SLIs/SLOs (latency, error rate) and alert on error-budget burn; add structured security audit logs.
How do you test complex UX flows reliably with Playwright/Cypress?
Use data-test IDs, stub flaky network dependencies where appropriate, and run against seeded databases. Parallelize specs, record traces/videos on failure, and quarantine flaky tests with auto-retry plus root-cause tracking.
What principles guide your contributions to an open-core project like Mattermost?
Public, small, well-scoped PRs with thorough tests, docs, and migration notes; follow coding standards and ADRs. Maintain backward compatibility, add telemetry where relevant, and engage in reviews/issues transparently.

📋 Job Summary

Mattermost is hiring a Software Engineer II in Germany to build secure, high-impact collaboration tools for defense, intelligence, and critical infrastructure sectors. You'll work full-stack with Go, TypeScript, React, and PostgreSQL, contributing to one of the largest open-source projects in its space. This fully remote role offers the chance to shape mission-critical workflows, mentor peers, and work with cutting-edge AI dev tools in a highly collaborative, global team. Join a company where engineering meets purpose.